Production of algae oils for refinement to create diesel fuels has been produced in open ponds using waste water as a food for the algae. Various approaches of algae production are known in the art. Photobioreactors have been described using shallow lagoons agitated with one or several paddle wheels. The photobioreactors of this first generation have the disadvantage of offering poor productivity to the seasonal and daily climatic variations and are thus to be confined to tropical and subtropical areas. They also have the disadvantage of being prone to a variety of contaminations including other algae species.
Other approaches to algae production have emerged over the past years. An example is the use of closed cultivating systems which have gained popularity because they address most of the limitations of the conventional shallow lagoon designs. The most popular closed cultivating systems are the tubular photobioreactors whose configuration allows high production rates due to the optimization of their light path, their temperature control and their culture mixture. This second generation of photobioreactors allows for an automated control and a more effective management. It also allows the pH of the culture medium to be lowered. Examples of tubular photobioreactors are shown in U.S. Pat. Nos. 5,137,828; 5,242,827 and 6,174,720. These closed loop systems require many supplements to be added to provide nutrients for algae growth.
Artificial light has been applied as an energy source for the growth of microalgae in Photobioreactors of various shapes. Examples of these photobioreactors are provided in U.S. Pat. Nos. 5,104,803 and 5,614,378. Adhesions of microalgae occur in a natural manner, particularly on the walls where light is emitted. The effect of adhesion of microalgae on the photobioreactor wall causes a reduction in the culture exposed to the light and raises the risks of contamination.
Although many photobioreactors have been proposed in the prior art, and there have been attempts to create diesel fuel using algae feeding on waste water, there is still a need for an improved diesel photobioreactor that enables volume production efficiencies at a cost effective basis for a commercial application.
Therefore, a need exists to overcome the problems with the prior art as discussed above.